As an automatic recognition technique enabling data transmission through radio communication, RFID is spreading. For example, the RFID comprises an ID tag capable of storing information, a reader/writer performing reading and writing of information in the ID tag and a host performing management of the information read by the reader/writer and the like.
Unique ID information is allocated to each ID tag, and therefore, in commodity distribution and the like, by attaching the ID tag to a commercial product and distributing the same, traceability of each commercial product can be performed efficiently.
However, in the RFID, since read/write of data is performed in a non-contacting manner, such a problem with security may occur that when a person holds an ID tag, behavior of the person is traced by a third party without his/her knowledge.
As a technique for preventing acquisition of information in the ID tag by a third party, for example, such a technique is known that a communication distance of the ID tag is reduced by shifting impedance matching between an antenna and a rectification circuit generating a power source voltage of the ID tag, increasing a consumption current in the rectification circuit consciously or the like.
As a technique of communication distance reduction of the ID tag of this kind, for example, a technique changing a communication response setting value by command data from an external communication device, changing an inside parameter corresponding to the same influencing a communication response distance and changing the communication response distance according to the parameter (see Japanese Patent Application Laid-Open Publication No. 2006-185234 (Patent Document 1)), a technique reducing a communication response distance by connecting a resistor or the like between an antenna and a reference potential VSS to shift impedance matching (see United States Patent Application Publication No. 2006/0145851 (Patent Document 2)) and the like exist.